More than one unapproved pharmaceutical ingredient was found in 20 percent of those supplements.

The presence of prescription medicines, often at unknown concentrations, means these supplements are essentially “unapproved drugs” that could be harmful to users’ health, according to researchers.

“These products have the potential to cause severe adverse health effects owing to accidental misuse, overuse, or interaction with other medications, underlying health conditions, or other drugs within the same dietary supplement,” researchers led by Madhur Kumar of the California Department of Public Health Food and Drug Branch, was quoted as saying by CNN.

For the study, published in the journal JAMA Network Open, Kumar and his co-authors reviewed the FDA’s Tainted Products Marketed as Dietary Supplements-CDER database for 2007 through 2016.

Most of the adulterated products, about 45 percent, were marketed for sexual enhancement, weight loss (about 41 percent) or muscle-building (12 percent).

Drugs found in sexual enhancement products included sildenafil, tadalafil, and vardenafil, all active ingredients in prescription medications intended for erectile dysfunction, which, when overused, can cause serious damage to the blood vessels.

The most common pharmaceutical ingredients detected in adulterated weight loss products were sibutramine, which was removed from the US market in 2010 due to cardiovascular risks, and the laxative phenolphthalein. Many of the adulterated muscle building products contained undeclared anabolic steroids, which, when abused, can lead to mental problems in the short term and kidney problems, liver damage and heart problems in the long term.

Other drugs found in the adulterated supplements include antidepressants and antihistamines, both of which may have side effects and interact with other medications.

“Only 360 of 746 (48 percent) were recalled, leaving the majority of adulterated supplements, more than 350 products, available for sale,” Cohen said.

Thus, according to Cohen, “more than FDA action will be required to ensure that all adulterated supplements are effectively and swiftly removed from the market.”